Conventional web converting equipment uses some sort of transport mechanism for moving the web at high rates of speeds through a series of processing stations. Typically such processing stations includes corrosive environments through which the web must be transported. For instance, in existing photographic film processors used to develop and fix photosensitive elements which are subjected to x-ray, visible and other radiation, the web is transported via a series of rollers defining a web transport path through a sequence of processing stations and then on to final processing in which the web is washed and then dried.
Other well known types of web processing applications in which a transport device may be employed include automatic processing of the media for thermal, ink jet or silver halide-based photographic printing, and the like. In these instances, an apparatus automatically transports sheets or webs or strips of photosensitive films, photosensitive papers or specially coated papers or plain papers. For photosensitive elements, this apparatus transports from a feed end of a film transport path, through a sequence of chemical processing tanks in which the media is developed, fixed, and washed, and then through a dryer to a discharge or receiving end. Processing apparatus of the type described typically has a fixed film (media) path length, so final image quality depends on factors including transport speed which determines length of time the media is in solution, and the temperature and composition of the processing chemicals.
It is well known that most, if not all, of the components that are exposed to harsh chemicals in a photographic film processor or a thermal printer or an ink jet printer are made from AISI 300 series stainless steel or engineering plastic for reasons of mechanical strength, lower cost, and relatively good corrosion resistance. Engineering plastics are generally used as bushings and gears because of their relatively low coefficient of friction against stainless steel.
Furthermore, it is also well known that photographic transport apparatus exposed in normal ambient conditions are also prone to wear and corrosion because of the abrasive and corrosive nature (depending on their relative humidity) of the photographic elements. Although stainless steel is widely used, stainless steel shafts, for example, despite being considerably strong and corrosion resistant, are prone to wear with time and are also susceptible to corrosion when exposed to harsh chemical environments, such as "fixer" solution for developing photographic films.
Skilled artisans are further aware that a host of engineering plastics reinforced with glass and carbon fibers or other hard inorganic particles may be used to improve the strength and wear resistance at the expense of corrosiveness. Another problem arises with plastic components in a fluid environment is that they tend to swell and become dimensionally unstable. For the reasons mentioned above, it is apparent that there is a need for processing apparatus composed of materials which will endure the harsh chemical environments and at the same time will be compatible with other components of the apparatus thereby enhancing the service life of the processing apparatus.
Experience indicates that structural ceramics like silicon carbide, alumina, zirconia and zirconia-alumina composites offer many advantages over conventional engineering materials, especially metals and plastics, to form bushings, gears and shafts elements, including many other ceramics and ceramic metal composites (also referred to as cermets). In order to achieve a longer service life from such elements, an ideal materials combination for shafts, bushings and gears needs to be made. Many ceramics and cermets are hard and, as a result, are wear resistant. Although ceramic is relatively brittle, it can be used as a bushing in appropriate combination with other engineering materials.
Therefore, despite some progress that has been made in web processing apparatus there nonetheless persists a need for such apparatus for processing photographic media that has bushing/shaft elements made of superior wear, abrasion and corrosion resistant materials which are cost-effective and easy to manufacture. Further, a need persists to employ ceramic gears in combination with ceramic bushing/shaft assemblage that has superior wear and abrasion and corrosion resistance and manufactured using net-shape technology.